1. Field of the Invention
The present invention relates to a camera system including: an optical unit having an image-taking optical system for forming an image based on subject light; and a camera main unit to which the camera unit is detachably attached and which applies predetermined signal processing to image data.
2. Description of the Related Art
Conventionally, there is known a lens-interchangeable camera composed of: a camera main unit having an imaging device; and an interchangeable lens unit having a shooting lens and attached to the camera main unit when the camera is in use. In this type of camera, subject light coming through the shooting lens of the lens unit is received on the imaging device of the camera main unit so that the imaging device can generate image data representing an image based on the subject light. This type of camera has the advantage of reusing interchangeable shooting lenses conventionally employed in a single-lens reflex camera that records an image on a silver-salt film.
In this case however, if, for example, a large expensive shooting lens having an excellent optical property is attached to a camera main unit containing a small low-solution imaging device, the shooting lens capable of precisely forming an image based on subject light cannot be fully utilized because the imaging device is incapable of reading the subject light accurately. To solve this problem, there is developed a lens-interchangeable camera composed of: a camera main unit; and a lens unit having a shooting lens and imaging device and attachable to the camera main unit (for example, refer to Japanese Patent Application Publications No. 10-191122, No. 2000-50138 and No. 2000-106640). According to the lens-interchangeable cameras disclosed in these publications, the lens unit has a built-in charge-coupled device (CCD) suitable for the size and optical property of a shooting lens, thereby obtaining a high-quality image by making full use of abilities of the shooting lens.
By the way, if a user presses the shutter button of a lens-interchangeable camera without attaching a lens unit to a camera main unit, there may be obtained a blurred image on which a subject cannot be identified. When it comes to the lens-interchangeable cameras disclosed in the above-described publications, if a user presses the shutter button without attaching the lens unit to the camera main unit, it is impossible to obtain an image because the CCD is built in the lens unit side. Considering such situations, Japanese Patent Application Publication No. 2000-152070 discloses a lens-interchangeable camera configured to switch the processing mode representing the processing by the camera to a mode other than a shooting mode upon removal of the lens unit from the camera main unit. For example, this camera forcibly switches the processing mode to a mode such as a playback mode for playing back images upon removal of the lens unit, which makes it possible to prevent occurrence of undesirable situations in which: a user obtains a useless image by pressing the shutter button without being aware of the lens unit being removed, a user misses the right moment to shoot an image, and the like.
Removal of the lens unit is likely to take place when a user wants to change the value in a zoom range etc. during shooting operation for shooting an image of a subject, and the user usually restarts the shooting operation after changing the lens unit. In this situation, it is desirable to restart the shooting operation immediately after changing the lens unit. However, such a quick restart cannot be realized by the method described in Japanese Patent Application Publication No. 2000-152070. In this method, the processing mode is switched to the playback mode etc. upon removal of the lens unit and therefore, a user needs to manually switch the playback mode to the shooting mode after changing the lens unit in order to restart the shooting operation, which requires time and effort.